Wide band boost regulator power supply

ABSTRACT

A power supply which, in one embodiment, provides to a load a relatively constant DC (direct current) output voltage at a voltage level equal to or greater than that being supplied from a variable DC voltage source. The power supply includes a first switching circuit controlled by a voltage sensing circuit to allow energy to be transferred from a current storage device to a voltage storage device to maintain the amplitude of the output voltage within predetermined levels, and also includes a second switching circuit controlled by a current sensing circuit to allow the amplitude of circuit to be maintained within predetermined limits.

0 United States Patent 1151 3,641,422 Farnsworth et al. Feb. 8, 1972WIDE BAND BOOST R GUL O 3,327,202 6/1967 M1115 ..323/22 T POWER SUPPLY3,381,202 4/1968 Loucks et al. ..32l/2 1 [72] Inventors: Robert P.Farnsworth, 12612 Indianapolis, 3 2 222: 3 24 Los Angeles Calif. 90066;Dennis G.

44 Sana" Los Angeles Primary Examiner-A. D. Pellinen Attorney-James K.Haskell and Walter J. Adam [22] Filed: Oct. 1, 1970 [21 Appl. No.:77,168 [57] ABSTRACT A power supply which, in one embodiment, providesto a load Related Apphcahon Dam a relatively constant DC (directcurrent) output voltage at a [63] Continuation-impart of Ser. NO.884,858, Dec. 15, voltage level equal to or greater than that being ppfrom 1969, abandoned. a variable DC voltage source. The power supplyincludes a first switching circuit controlled by a voltage sensingcircuit to [52] U.S. Cl .323/8, 321/2, 323/17, allow en rgy to be t n frred from a current storage device to 323/20, 323/22 T, 323/38, 323/DIG.1 a voltage storage device to maintain the amplitude of the out- [51]Int. Cl. ..G05f1/56,G05f 1/60 put voltage within predetermined levels,and also includes a [58] Field of Search ..32l/2; 323/4, 8, 17, 20, 22T, second switching circuit controlled by a current sensing cir- 323/22SC, 38, 94 H, DIG. l cuit to allow the amplitude of circuit to bemaintained within predetermined limits. [56] References Cited 12 Claims,9 Drawing Figures UNITED STATES PATENTS 3,523,239 8/1970 Heard .323/203/ 2'9 4 .1 i I L aezawr 6 .bt/t/sm T Q 1 C/ecu/T' l 1 i i 04 126 :0 /7I ,2 2 55 27 c/recu/f 25 l /5 WIDE BAND BOOST REGULATOR POWER SUPPLYThis is a Continuation-in-part of application, Ser. No. 884,858, filedDec. 15, I969, now abandoned. The invention herein described was made inthe course of or under a contract with the United States Army.

BACKGROUND OF THE INVENTION This invention relates to power supplies andparticularly to a wide band boost regulator power supply.

Conventional regulator power supplies are of three types. One type is ahigh efficiency regulator which provides an output voltage equal to orless than the input voltage. This type of supply is unusable where theinput voltage is less than the desired output voltage. A second type isthe direct current to direct current (DC-DC) converter for providing anunregulated output voltage which is related to the input voltage by somefixed ratio. The third type is a boost regulator which regulates theoutput voltage at a higher level than the input voltage. However,changes or transients in the input or output circuits requireappreciable timefor recovery and result in output transients from theregulator. The inherent response of the regulator control loop must ofnecessity be limited for stable operation.

None of the prior art systems previously discussed provide both avoltage increase and wide bandwidth or rapid loop control type ofregulation.

SUMMARY OF THE INVENTION Briefly, an improved wide band boost regulatorpower supply is provided which utilizes a voltage sensing circuit toallow a constant current source to increase the output voltage when theoutput voltage is low and to prevent any further increase in the outputvoltage beyond a predetermined level by bypassing the constant currentsource back to itself when the output voltage has reached or exceededthe predetermined voltage level. The constant current source utilized inthis invention includes a current sensing circuit coupled to aninductive device to control the operation of a switching circuit as afunction of the amplitude of the current in order to maintain the levelof the current within predetermined limits.

It is therefore an object of this invention to provide an improved wideband boost regulator power supply.

Another object of this invention is to provide a power supply fordeveloping a relatively constant DC voltage from a variable DC source bya highly efficient means.

Another object of this invention is to provide a power supply whichincreases the voltage supplied by a variable DC source so as to providea constant output voltage which is at all times equal to or greater thanthe input voltage.

Another object of this invention is to provide a regulated power supplywhich produces a constant output voltage while preventing significantvariations in the output voltage due to transient load or input changes.

A further object of this invention is to provide a regulated powersupply which produces a plurality of different output voltages isolatedfrom the input power source.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features andadvantages of the invention, as well as the invention itself, willbecome more apparent to those skilled in the art in the light of thefollowing detailed description taken in consideration with theaccompanying drawings wherein like reference numerals indicate like orcorresponding parts throughout the several views wherein:

FIG. I is a schematic circuit and block diagram of the regu' lated powersupply in accordance with one embodiment of this invention.

FIG. 2 is a graph which illustrates the response characteristics of theswitching circuit controlled by the voltage sensing circuit of FIGS. 1,4 or 9.

FIG. 3 is a graph which illustrates the response characteristics of theswitching circuit controlled by the current sensing circuit of FIGS. 1,4 or 9.

FIG. 4 is a schematic circuit and block diagram of the regulated powersupply in accordance with a second embodiment of this invention.

FIG. 5 is a schematic circuit diagram of the power supply in accordancewith the second embodiment of this invention.

FIG. 6 is a schematic block circuit diagram of the power supply of FIG.1.

FIGS. 7 and 8 show a different type of current sensing circuit which maybe used in the embodiments of FIGS. 6 and 5, respectively.

FIG. 9 is a schematic circuit and block diagram of the regulated powersupply in accordance with a third embodiment of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to thedrawings, FIG. 1 illustrates a schematic circuit and block diagram inaccordance with one embodiment of the invention. The embodiment of FIG.1 can best be explained by also referring to FIGS. 2 and 3. In themechanization of the power supply of FIG. 1 an anticipated low voltageextreme of the input and output operating conditions was taken intoconsideration in order to provide a substantially transient freeregulation during expected input voltage transients which may lower anominal,| -24-volt input applied between a terminal 11 and a groundedterminal 13 to, for example, 6 volts for up to milliseconds or evenlonger. Furthermore, this invention will also maintain regulation of theoutput voltage during the time that these expected transients increasethe nominal,+24-volt input up to as high as +26.7 volts, for example.Any deviations below or above this nominal +24-volt level could becaused by line or load voltage transients. The circuit of FIG. 1 istherefore designed so that with an input under +6 volts, which is thelowest anticipated operating condition encountered for this particularuse, the current being supplied to the load 15 would be approximately 2amperes, which is the current required by the load I5 for normaloperation. Furthermore, the output voltage will regulate within aselected range, for example, of from +24 to +26 volts throughout theexpected input voltage range of from +6 volts to +26.7 volts. It shouldbe understood that the invention is also applicable to a negativevoltage power supply or to other operating conditions by proper designconsiderations, such as changing the location or size of components. I

In operation, unregulated voltage at a nominal level of, for example,+24 volts is applied from an unregulated voltage source (not shown) tothe input terminals 11 and 13 of the power supply of this invention.This unregulated voltage source supplies power via a charging currentthrough a serially coupled combination consisting of a current sensingcircuit 17, a constant current source or inductor l9, and a diode 21 tothe load 15, which may include a resistor R The other side of the load15 is returned to the terminal 13 through a ground lead 23. A capacitor25 is coupled in parallel with the load 15 to absorb fluctuations orchanges in the charging current applied to the load 15 in order to allowa constant power to be delivered to the load 15.

A voltage sensing circuit 27, coupled across the capacitor 25 in orderto sense the output voltage, controls the operation of a switch orswitching circuit 29 in response to the sensed output voltage. Theswitch 29, which is coupled across the serially coupled current sensingcircuit 17 and inductor 19 combination, is closed by the voltage sensingcircuit 27 when the output voltage equals or exceeds an upper limit E(FIG. 2) of, for example, +26 volts and is opened by the voltage sensingcircuit 27 when the output voltage decreases to or below a lower limitE, (FIG. 2) of, for example, +24 volts. The switch 29 is designed toonly allow a unidirectional flow of current therethrough. For thisreason the switch 29 is illustrated in FIG. 1 as including a diode 31coupled in series with a set of contacts 33.

The current sensing circuit 17 senses the current through the inductor19 and in response thereto controls the operation of a second switch orswitching circuit 35, which is coupled between the ground lead 23 andthe junction of the inductor 19 and the anode of the diode 21. When thecurrent through the inductor 19 is equal to or below a first currentlevel I (FIG. 3) of amperes, for example, the current sensing circuit l7closes the switch 35. The closure of the switch 35 reverse-biases thediode 21 to prevent the capacitor 25 from discharging through the closedswitch 35, reverse-biases the diode 31 to disable the switch 29, andprovides a low impedance direct current (DC) return path to the inputterminal 13 in order to allow the current through the inductor 19 tobuild up to a second current level 1 (FIG. 3) of, for example, 12amperes. When the current through the inductor 19 reaches or exceedsthis second current level I the current sensing circuit 17 opens theswitch 35. The opening of the switch 35 removes the low impedance returnpath to the input terminal 13 to prevent any further increase in theinductive current, forward-biases the diode 31 to enable the switch 29,and, if the set of contacts 33 of the switch 29 is open, forwardbiasesthe diode 21 in order to allow power to again be applied to the load 15.During the period of time that the switch 35 is closed, the discharge ofthe capacitor 25 supplies power to the load 15. During the period oftime that the switch 35 is open, the excess in charging current beingapplied to the load 15 charges the capacitor 25 so that the outputvoltage is regulated between the lower and upper limits of +24 volts and+26 volts, respectively.

In initial operation when the nominal +24 volt input is first applied tothe power supply, the switch 29 is open due to the low output voltagesensed by the voltage sensing circuit 27, and the switch 35 is closeddue to the low inductor 19 current sensed by the current sensing circuit17. As previously described, the closure of the switch 35 reverse-biasesthe diodes 21 and 31, by grounding their anodes, in order to prevent anypower from being delivered to the load 15 from the inductor 19 while thecurrent through the inductor 19 is increasing to the 1 level of l2amperes.

As illustrated in FIG. 3, with the closure of switch 35, the currentflowing through the inductor 19 starts building up according to a linearramp, which is determined by the inductance of the inductor 19 and theamplitude of the DC input voltage. This linear increase of currentthrough the inductor 19 in relation to time causes a correspondingincrease in the current that is sensed by the current sensing circuit17. When the current sensing circuit 17 senses that the current flowingthrough the inductor 19 has reached the upper level I as shown in MG. 3,the current sensing circuit 17 causes the switch 35 to open. The openingof switch 35 interrupts the buildup of current through the inductor 19,causing the magnetic field or flux that had been built up around theinductor 19 to start to collapse. This collapsing magnetic field cutsacross the inductor 19 and induces thereacross a back electromotiveforce (EMF) or voltage which has a polarity that is series-aiding withthe +24 volt input and tends to keep current flowing in the samedirection through the inductor 19. With the opening of the switch 35,the diodes 21 and 31 become forward-biased and current starts flowing inthe load 15 through the diode 21.

Since the input, as specified before, is at a nominal +24 volts, thereis a very small and negligible voltage drop across the inductor 19..Therefore the flux in the inductor 19 changes very slowly, the currentdecays very slowly, and most of the power being supplied to the load 15and capacitor 25 is supplied from the unregulated voltage source coupledto the input terminals 11 and 13. The current being supplied to theparallel-coupled load 15 and capacitor 25 after the current sensingcircuit 17 opens the switch 35 is initially about 12 amperes. Thecurrent required by the load 15 is based upon the voltage drop acrossthe capacitor 25 and the impedance of the load 15. At the time of theinitial turn-on no voltage was developed across the capacitor. Since atthis time the load 15 does not require any current, the current beingsupplied starts charging the capacitor 25. As the capacitor 25 charges,the load 15 starts requiring current, but not at the amplitude beingsupplied to the parallel-coupled load 15 and capacitor 25. Even duringnormal operation the current required by the load 15 is approximately 2amperes. Therefore, current is being supplied faster than the load 15can absorb it. As a result, the voltage across the capacitor 25 startsincreasing due to this charging current.

When the charging current charges the capacitor 25 to or above the +26volt level, the voltage sensing circuit 27 causes the switch 29 toclose. When the switch 29 closes, the current through the inductor l9circulates through itself via the switch 29 in order to prevent anyfurther increase in the output voltage. The capacitor 25 then starts toslowly discharge through the load 15. When the output voltage, as sensedby the voltage sensing circuit 27, decreases to or below the +24-voltlevel, the voltage sensing circuit 27 opens the switching circuit 29 toenable the capacitor 25 to be recharged to the +26-volt level.

In normal operation, whenever the unregulated input voltage beingapplied between the terminals 11 and 13 is low enough to drop the outputvoltage to or below +24 volts, the cycle will repeat itself with theoutput voltage varying between the +24-volt and +26-volt limits.However, the average output voltage does not change during this cyclingoperation, although there is a sawtooth, or ripple voltage, on theoutput which varies between the +24-volt and +26-volt limits. It shouldbe noted at this time that the frequency of cycling as well as the rangeof the voltage limits could be changed, if a different operation isdesired, by changing the values of the components to vary the circuitparameters. For example, a decrease in the operational limits of thevoltage sensing circuit 27 will increase the ripple frequency anddecrease the amplitude of the output ripple, whereas a decrease in thevalue of the capacitor 25 will increase the ripple frequency but notaffect the amplitude of the output ripple.

In another operational condition, there will be no cycling operation,and hence no ripple, whenever the output voltage is prevented from goingbelow +24 volts. This condition occurs whenever the level of the inputvoltage remains within the range of +24.7 volts to +26.7 volts. Withinthis range the out: put voltage will stabilize at a voltage level equalto the input voltage minus the voltage drop across the diode 21, whichis approximately 0.7 volt.

Assuming, after normal operation is achieved, a transient voltage dropsthe input voltage between terminals 11 and 13 to a +6 volt level. Atthis time the circuit could be in any one of four states of operation.These four states of operation will now be discussed.

In the first state, assume that the switches 29 and 35 are both openwhen the transient voltage occurs. The current through the inductor 19starts decreasing since it is flowing through the diode 21 into the load15. Since the current flowing from the inductor 19 is greater than 10amperes the output voltage is increasing at this time. With the outputvoltage increasing, the switch 29 remains open until the output voltagereaches the upper limit of +26 volts, at which time the switch 29 closesand bypasses the inductor 19 back to itself. In the event that thecurrent through the inductor, as sensed by the current sensing circuit17, decreases to the level I of FIG. 3 before the output voltage hasincreased to the upperlirnit of +26 volts, the switch 35 is closed bythe current sensing circuit 17, and the current through the inductor 19starts increasing until it reaches the level. At this time the currentsensing circuit 17 opens the switch 35, thereby allowing the currentthrough the inductor 19 to continue charging the capacitor 25 to theupper limit of +26 volts,

In the second state, assume that the switch 29 is open and the switch 35is closed when the transient voltage occurs. At this time, the diodes 21and 31 are both reverse-biased, there is no current from the inductor l9flowing into the output, and

the capacitor 25 is slowly discharging through the load 15. The currentin the inductor 191s increasing from to 12 amperes, but at a slower ratesince the input voltage has been reduced to +6 volts by the transient.When the current through the inductor 19 reaches the 1 level of 21amperes, the current sensing circuit 17 causes the switch 35 to open. Atthis time the power supply reverts to the first state of operation,which allows the inductor 19 to deliver a charging current to thecapacitor 25 to increase the output voltage to the +26 volt limit.

In the third state, assume that the switch 29 is closed and the switch35 is open when the transient voltage occurs. The cur rent through theinductor 19 is circulated back to itself through the switch 29. Theoutput voltage is decreasing at this time not because of the transientvoltage but because the closure of the switch 29 allows the capacitor 25to discharge through the load 15. Therefore, the transient voltage hasno effect at all on the output voltage during this operation. With theoutput voltage decreasing, the switch 29 remains closed until the outputvoltage decreases to a +24 volts, at which time the voltage sensingcircuit 27 causes the switch 29 to open. Since at this time both of theswitches 29 and 35 are open, the inductor 19 starts delivering acharging current to the load and to the capacitor 25, as previouslydiscussed in the operation for the first state.

in the fourth state, assume that the switches 29 and 35 are both closedwhen the transient voltage occurs. The closure of the switch 35reverse-biases the diodes 21 and 31, thereby preventing the current inthe inductor 19 from flowing either through the now closed set ofcontacts 33 of the switch 29 or through the load 35. The current throughthe inductor 19 is in the process of increasing from the I, level to theI level, as shown in FIG. 3. Capacitor is also slowly dischargingthrough the load 15. if the current through the inductor 19 increases to12 amperes before the output voltage drops below +24 volts, the currentsensing circuit 17 causes the switch 35 to open and the subsequentoperation is the same as described for the third state. If, however, theoutput voltage decreases below +24 volts before the current through theinductor 19 increases to the 1 level, the switch 29 opens and thesubsequent operation is the same as that described in relation to thesecond state. Furthermore, if the current through the inductor 19reaches the 1 level at the same time that the output voltage drops below+24 volts, both of the switches 29 and 35 open and the subsequentoperation is the same as that described in relation to the first state.

If in operation the transient is present at the input terminals 11 and13 for an indefinite period of time, the current through the inductor 19builds up the 1 level of 12 ampercs and the subsequent opening of switch35 by tire current sensing circuit 17 allows the capacitor 25 to berecharged before there is an appreciable drop in the output. This systemtherefore provides transient-free protection at an output voltage levelbetween the +24-volt and +26-volt limits as long as the input voltage isin the range from +6 volts to +267 volts. Furthermore, since the circuitof FIG. I reacts instantaneously, there is no transient recovery period.

Referring now to H6. 4, a second embodiment of the invention isillustrated. In this embodiment a transformer 37 is utilized in place ofthe inductor 19 of FIG. 1 with a switching circuit or switch 39,corresponding to the switch 29, being placed in series with thesecondary winding of the transformer 37. A switching circuit or switch40, similar to the switch 35 of FIG. 1, is serially coupled between theprimary winding of the transformer 37 and the ground lead 23. A currentsensing circuit 4 1 which will be described in more detail later, sensesthe flux in both windings of the transformer 37. Since the flux isdependent upon the ampere-turns of both windings of the transformer 37,with the turns ratio of the transformer being fixed, the current sensingcircuit 41 will sense the current in the transformer 37 because thecurrents in both windings affeet the flux coupling the windings. Theremaining components of FIG. 4 may be identical to their equivalentcomponents in FlG. 1 and therefore have the same reference numerals astheir equivalents in FIG. l.

in operation the voltage sensing circuit 27 controls the operation ofthe switching circuit 39 and the current sensing circuit 41 controls theoperation of the switching circuit 40 in the same manner as described inrelation to FIG. I. The waveforms shovm in FIGS. 2 and 3 are equallyapplicable to the second embodiment as shown in FIG. 4.

A more detailed explanation of the operation of the embodiment of FIG. 4will now be given by referring to FIG. 5. The embodiment of FIG. 5utilizes a Hall generator or Hall device similar to the HS-Sl Halltron,which is manufactured by Ohio Semiconductors Incorporated and describedand illustrated in its publication on the Halltron HS-5 l. The Hallgenerator 101 is a device which is based upon the Hall effect, which inturn arises when a conducting material is placed in a magnetic fieldperpendicular to the direction of the current flow, thereby developing avoltage across the material in a direction perpendicular to both themagnetic field and the current. This voltage is called the Hall voltageand is proportional to the instantaneous product of the magnetic fieldand the current passing through the element. The Hall device 101 isplaced in the core of transformer 37 and senses the amount of currentpassing through both of the primary and secondary windings of thetransformer 37 by sensing the amount of flux or magnetic field in thetransformer 37. The transformer 37 is wound to have a phase reversal asindicated by the black dots between the primary and secondary windingsand has a fixed turns ratio between these windings. The flux beingsensed is proportional to the total ampere turns. However, the turnsratio of the transformer 37 is fixed. Therefore the flux being sensed isproportional to the amperes flowing in both of the primary and secondarywindings, since both contribute to the total flux being sensed.

More specifically, an unregulated input voltage at a nominal +24-voltlevel, but which may vary from +6 to +26.7 volts, is applied between theinput terminals 11 and 13 of the power supply of FIG. 5. The terminal 13is placed at a reference potential or ground in order to provide a DCreturn path. The input terminal 11 is connected to the collector of anNPN- transistor 103 in the current sensing circuit 41. The transistor103 has its emitter coupled through the Hall device 101 and through aresistor 105 to ground in order to supply a control current to the Halldevice 101. The base of the transistor 103 is coupled through resistor107 to a source of potential of, for example, +15 volts. A zener diode109 is connected between the base of transistor 103 and the referencepotential in order to stabilize the base to ground potential for thetransistor 103 so that a constant control current will flow through thetransistor 103, the Hall device 101, and the resistor 105 to ground.Since the emitter current of transistor 103 supplies a constant controlcurrent to the Hall device 101 and since the Hall device is mounted inthe core of the transformer 37, the Hall device will generate a Hallvoltage which, as mentioned before, is proportional to the instantaneousproduct of the magnetic field and the control current passing throughthe Hall device 101. Since the control current is held constant the Hallvoltage appearing at the output terminals 110 and 111 is proportional tothe flux thattintercepts the surface of the Hall device 101. The outputterminals 110 and 111 of the Hall device 101 are respectively coupledthrough resistors 113 and 115 to inverting and noninverting terminals 3and 2, respectively, of a comparator 117. The comparator 117 may be aFairchild uA7l0, High Speed Comparator, manufactured by FairchildSemiconductor Corporation and described and illustrated in its handbook,Fairchild Semiconductor Linear 1ntegrated Circuits, ApplicationHandbook. A resistor 119 is coupled between the input terminal 2 andoutput terminal 7 of the comparator 1117 and operates, in conjunctionwith the resistor R15, to form a positive feedback for the currentsensing. This positive feedback allows the current sensing circuit 41 toturn on the switching circuit 40 when the current being sensed by thecurrent sensing circuit 41 drops to or below 10 amperes and to not turnthe switching circuit 411 off again until the current being sensedequals or exceeds 12 arnperes.

The resistor 121 is coupled between the input terminal 3 of thecomparator 117 and the +15 volt source so that the voltage drop acrossthe resistor 113 will represent the amount of the nominal currentdesired in the sensing circuit. The values of the resistors 113, 115,119 and 121 are determined by the characteristics of the Hall device 101in a particular design and also by the way the Hall device is insertedinto the transformer 37.

The comparator 117, which receives the Hall voltage developed at thetenninals 110 and 111 of the Hall device 101 at its input pins 3 and 2,will develop a voltage at its output pin 7 which indicates whether thecurrent being sensed is high or low. If the current being sensed by thesensing circuit 41 is at or below the l level of 10 amperes, the voltageat output pin 7 of the comparator 117 will be in a low or negativevoltage state, which causes the switching circuit 40 to be turned on. Inorder for the comparator 1 17 to produce a negative voltage at itsoutput pin 7, the voltage at its pin 2 with respect to ground must beless than the voltage at its pin 3 with respect to ground. Under theseconditions the negative voltage at output pin 7 of the comparator 117will not couple through zener diode 125 into the switching circuit 3 5,since zener diode 125 will be rendered nonconductive by this negativeoutput voltage.

The anode of the zener diode 125 is coupled to ground through seriallyconnected resistors 127 and 129, which are located in the switchingcircuit 41). An NPN-transistor 131 has its emitter base region connectedbetween ground and the junction of the resistors 127 and 129. Since thezener diode 125 is rendered nonconductive under low sensed currentconditions, there will be no current flow flowing through the resistors127 and 129. Therefore, the transistor 131 will be in a cutoff conditionand its collector, which is returned through a resistor 133 to the+l-volt source, will be at a high positive voltage or logical one state.This logical one state is applied to the inverter 135 which develops alogical zero or low voltage level at its output in response to thelogical one state signal at its input. This low output voltage level isapplied through resistor 137 to the base of PNP-transistor 139. Theemitter of the transistor 139 is connected directly to the emitter oftransistor 14], which is connected as an emitter-follower and forms apart of a low voltage regulator for maintaining the emitter oftransistor 139 at a constant potential of, for example, 5 volts. Thebase of the transistor 139 is biased by the voltage applied from theemitter of transistor 141 through a resistor 143. The collector of thelow voltage regulator transistor 141 is coupled to the input terminal 11and receives the unregulated input voltage therefrom. For receiving theproper bias, the base of the transistor 141 is connected to the junctionof serially connected resistor 145 and zener diode 147 which arerespectively connected between the +l5-volt source and ground. Theemitter of transistor 141 is returned to ground through bleeder resistor149. A capacitor 151 is coupled across the bleeder resistor 149 in orderto stabilize the 5-volt output at the emitter of transistor 1411. Thebase potential of the transistor 141 is regulated at a +5-volt level dueto the zener diode 147. As a result the emitter of transistor 141 holdsthe emitter of the transistor 139 at a +5-volt level. Therefore theoutput of the transistor 139 is directly dependent upon the state of theoutput of the inverter 135.

Since the output of the inverter 135 is at a low voltage level orlogical zero state under low current conditions, the PNP- transistor 139conducts through its collector load resistor 153 to ground developing anoutput signal at a high voltage level or logical one state. Thecollector voltage of transistor 139 is applied through resistor 155 tothe base of transistor 157. The transistor 157., in conjunction withtransistor 159, operates as a Darlington-connected stage in that thecollectors of the transistors 157 and 159 are connected together throughthe secondary winding of transformer 161. A resistor 163 is coupledacross the secondary of the transformer 161 and between the collectorsof the transistors 157 and 159 in order to protect the transistor 157from damage from transient voltage during the cutoff of transistor 157,which will be discussed later.

The high level signal, that is applied from the collector of thetransistor 139 through resistor 155 to the base of the transistor 157,causes the transistor 157 to start conducting. The conduction of thetransistor 157 supplies current from the collector of transistor 157into the base of transistor 159, causing transistor 159 to startconducting. Upon the conduction of transistor 159, current flows fromthe input terminal 1 1 through the primary of transformer 37, throughthe primary of transformer 161, and through the collector emitter regionof the transistor 159 to ground. The conduction of current through theprimary of the transformer 161 causes a smaller current to flow throughthe secondary of the transformer 161,

since the transformer 161 may have a turns ratio of l to 10, for

example. With this tums ratio a current of l0 amperes flowing throughthe primary of thetransformer 161 will cause l ampere of current to flowor to circulate in the secondary of the transformer 161. If the basecurrentof the transistor 159 is one-tenth of the collector current ofthe transistor 159, then the transistor 157 will be in a saturatedcondition. With transistor 159 conducting at saturation, the collectorof the transistor 159 is eflectively placed at DC ground potential. Thevoltage drop across the primary of transformer 161 is negligible, sinceit is on the order of a few tenths of a volt. For this reason the bottomend of the primary of the transformer 37 is essentially grounded,thereby reverse-biasing the diode 21 to prevent the capacitor 25 fromdischarging through the transistor 159.

Since the top end of the primary of the transfonner 37 is connected tothe input terminal 11, it is at the nominal 24-volt level and currentstarts building up in the primary of the transformer 37. As the currentis building up through the primary of the transformer 37 a voltage isinduced in the secondary of the transformer. The transformer is wound tohave a phase reversal across the secondary, such that the inducedvoltage across the secondary reverse-biases diode 164, therebypreventing any current from flowing or circulating in the secondary ofthe transformer 37. As a result, the primary current consists of alinear ramp or linear increase of current with respect to time, which isdetermined by the inductance of the primary of the transformer 37 andthe amplitude of the DC input voltage. This linear increase of currentwith respect to time also causes the flux to increase in the core of thetransformer 37 in a linear fashion.

When the current flowing through the primary of the transformer 37 hasbuilt up to or above the upper l limit of l2 amperes, the flux sensed bythe Hall device 101 reaches the upper level. The Hall device 101 thenproduces an output voltage at its terminals and 111 such that, withrespect to ground, the voltage at pin 3 of the comparator 117 is lowerthan the voltage at pin 2 of the comparator 117. Therefore, the voltageat output pin 7 of the comparator 117 becomes sufficiently high to causethe zener diode to conduct through the resistor 127 and the base emitterregion of the transistor 131 to ground, thereby causing the transistor13] to start conducting. The conduction of the transistor 131effectively places its collector and the input to the inverter 135 at aground potential or a logical zero state. This logical zero state causesthe output of the inverter 135 to go to a high voltage state or alogical one state, which cuts off the transistor 139. The cutofl' of thetransistor 139 removes the drive to the transistor 157. As transistor157 starts to cutoff, the voltage at its collector begins to rise.Before the drive to the transistor 157 was removed, the transistor 157was in a charge-storage condition, which means that it was beingoverdriven beyond the normal saturation point. Therefore as thetransistor 157 starts to cut off, it can still supply drive to thetransistor 159 while it is beginning to cut off.

To shorten the tumoff time of the transistor 159, the collector-emitterregion of a transistor is connected across the 9 base-emitter region ofthe transistor 159. A series-parallel network, consisting of resistors167, 169, 171 and capacitor 173, is coupled between the collector oftransistor 157 and ground with the junction of the resistors 167 and 169being connected to the base of transistor 165 for controlling theoperation of this transistor.

As the transistor 157 starts to cut off, its collector voltage starts toincrease. This increase in collector voltage is capacitively coupledthrough capacitor 173 and resistor 171 to the base of the transistor 165in order to provide the turn-on drive to the transistor 165. Thetransistor 165 then starts conducting, thereby providing a shunt pathacross the base-emitter region of the transistor 159 in order to removethe stored base charge in the transistor 159 and provide more rapidturnoff of the transistor 159. As soon as the transistor 1S9 cuts off,the current flowing through the primary of the transformer 37 isprevented from flowing through the primary of the transformer 161. Theinductive effect of the transformer 37 causes the magnetic filed, whichhad been built up by the current flowing through the primary of thetransformer 37, to collapse and induce a back electromotive force (EMF)across the primary which tends to keep the current flowing in the samedirection as it had before. This back EMF forward biases the diode 21which then provides a path for current from the primary of thetransformer 37 to charge the capacitor 25 and deliver power to the load15. This current being supplied to the load 15 and capacitor 25 is inthe form of pulses. As a result, the capacitor 25 is used to absorb thefluctuation and allow a constant power to be delivered to the load 15.

Since under normal conditions the input voltage between terminals 11 and13 is nominally +24 volts and the output voltage across the load canvary within the range from +24 to +26 volts, there is a very small,almost negligible, voltage drop across the primary of the transformer37. Therefore the flux changes very slowly, the current through theprimary of the transformer 37 decays very slowly and most of the powersupplied to the load 15 is supplied by the input power between theterminals 11 and 13. As the primary current through the transformer 37decreases to the lower current level 1 of FIG. 3, or arnperes, the Halldevice 101 will sense this lower current level and produce an outputvoltage between its terminals 110 and 111 such that the voltage betweenpin 3 of the comparator 117 and ground is greater than the voltagebetween pin 2 of the comparator 117 and ground. As discussed before,with a low current level being sensed by the Hall device 101 theresultant low voltage level from output pin 7 of the comparator 117 willnot be applied through the diode 12.5, and the transistor 131 will cutoff. The high level output of the transistor 131 is inverted by theinverter 135 to turn on the transistor 139, which in turn turns on thetransistor 157, which in turn turns on the transistor 159. The tum-on ofthe transistor 159 a gain reverse-biases the diode 21 and allows thecurrent through the primary of the transformer 37 to build back up tothe 1 or IZ-ampere level, at which time the above sequence repeatsitself.

Now in this mechanization, it was postulated that the current requiredby the load was approximately 2 amperes, while the current that wasflowing through the primary of transformer 37 ranged between the 1 and 1limits of 10 to 12 arnperes. It should be obvious that if more currentwere required by the load 15 the circuitry could be modified by changingthe sizes of the components to achieve operation at currents other than.those discussed above. At the time that the transistor 159 is turned 05,the current flowing through the primary of the transformer 37 hasreached the IZ-arnpere limit and shortly thereafter the magnetic fieldbuilt up around the primary of transformer 37 collapses and causes thiscurrent to flow through the diode 21 and to the load 15 and to thecapacitor 25. Since the load only requires 2 amperes of current theexcess in current is used to charge the capacitor 25. In a sense thetransformer 37 is supplying current faster than the load can absorb it.As a result, the voltage across the capacitor 25 starts increasing,thereby increasing the output voltage.

The voltage sensing circuit 27 monitors the output voltage and operatesto regulate the output voltage between the approximate lirnits of 24 and26 volts. Serially connected resistors 175, 177, and 179 form a voltagedivider which is coupled across the load 15 in order to develop a sampleof the output voltage across the resistor 179. The voltage sensing forthe voltage sensing circuit 27 is done through the resistors 175, 177and 179 with resistor 179 feeding the sample of the output voltage intoinput pin 2 of a differential comparator 181. The comparator 181 may bea Fairchild A710, High Speed Comparator, like the comparator 117. Thecomparator 181 is protected from damage due to excessively hightransient conditions by the zener diode 182, which is connected betweenground and the junction of resistors and 177. The diode 182 does notconduct in any normal operation of the circuit. However, under sometransient conditions the unregulated input between terminals 11 and 13may rise to as high as, for example, +90 volts. In this event the diodewill start conducting during the period of the excessively high voltagetransient condition, thereby preventing damage to the comparator 181.

Pin 3 is the reference input for the differential comparator 181 and iscoupled through a network composed of resistors 183 and 184 and zenerdiode 185 to the +l5-volt source. This network provides a fixed voltagereference to pin 3 of the comparator 181. Resistor 183 compensates forthe impedance driving the other input on pin 2 of the comparator 181.Resistor 187, which is coupled between the noninverting input pin 2 andoutput pin 7 of the comparator 181 provides positive feedback for thecomparator 181 so as to add hysteresis to the control of the voltage.That is, when the voltage being sensed across the resistor 179 is toohigh, it exceeds the reference voltage being applied to pin 3 of thecomparator 181. The feedback through resistor 187 is such that theoutput voltage as sensed by resistors 175, 177 and 179 must decrease bysome relatively large amount, for example a 2-volt decrease from +26volts to +24 volts, before pin 2 will again cross over with pin 3 torepresent a low voltage condition.

When the output voltage across the capacitor 25 increases to or beyondthe +26-volt limit, the voltage on pin 2 will exceed the referencevoltage on pin 3 of the comparator 181, thereby causing a high outputvoltage to be applied from output pin '7 of the comparator 181 throughzener diode 189 and resistor 191 to provide the drive to turn onNPN-transistor 193. Resistor 195 is connected between the base of thetransistor 193 and ground in order to provide a path for the leakagecurrent in the transistor 193 and to desensitize the transistor 193 tonoise pickup. The transistor 193 will conduct whenever the outputvoltage equals or exceeds the upper voltage limit of +26 volts andcontinue to conduct until the output voltage has decreased to or below+24 volts at which time the transistor will be cut off.

The conduction of the transistor 193 through the resistor 197, locatedin the switching circuit 39, furnishes the base drive for PNP-transistor199, causing transistor 199 to start conducting also. emitter of thetransistor 199 is connected directly to the output while the base isconnected through a resistor 201 to the output. Resistor 201 takes careof leakage currents and desensitizes the operation of the transistor 199for noise purposes. Upon being turned on, the transistor 199 conductsthrough resistor 203 and through the base-emitter region of transistor205, at which time the transistor 205 starts conducting. Resistor 207,which is connected between the base and the reference potential,establishes a low impedance across the base-emitter junction of thetransistor 205 to provide rapid turnoff. The conduction of thetransistor 205 through the diode 164 and the secondary of thetransformer 37 completes the path to short out the secondary winding ofthe transformer 37. The total voltage drop across the secondary windingof the transformer 37 will now be equal to the diode drop across thediode 164 plus the saturated transistor drop across thecollector-emitter region of the transistor 205, which will beapproximately 1 volt or less.

The reflected impedance of the secondary shorts out the pri mary of thetransformer 37, thereby reverse-biasing the diode 21, which prevents thetransformer 37 from supplying additional current to charge the capacitor25 to a higher voltage.

It should be noted at this point that if the input voltage between theinput terminals 11 and 13 is high enough above .+24 volts toforward-bias the diode 21, the load current can be supplied directlyfrom the unregulated input between terminals 11 and 13 without theoperation of the regulator power supply.

To show how the power supply will regulate the output voltage between.+24 and +26 volts when the unregulated input voltage may be somewherebetween +6 and +26.7 volts, the worst possible condition will beconsidered, namely when the input voltage has been reduced to +6 voltsby some transient or even on a steady state basis. If at the time theinput voltage drops to +6 volts, the output voltage is above +24 volts,and they transistor 205 is conducting, the power supply will remaininoperative until the capacitor 255 has discharged sufficiently throughthe load 15 to decrease the output voltage to or below the +24 voltlower voltage level. At this time, as previously described, thetransistor 205 in the switching circuit 39 becomes nonconducting. Thecurrent in the transformer 37 will then be delivered in pulses to theload 15 and capacitor 25 according to the previously discussed operationof the current sensing circuit 41 and the switching circuit 410. Itshould be recalled that when the transistor 159 is first cut off thecurrent through the primary of the transformer 37 is at 12 amperes, anddecreases to amperes as it is supplied to the load and to charge thecapacitor 25. When the current through the primary of the transformer 37has decreased to 10 amperes, the Hall device will produce an outputsignal which, according to the sequence of operation previouslydescribed, will turn on the transistor 159 and allow the current in theprimary to build back up to the 1 or 12 ampere level.

Since the output voltage as developed across the capacitor 25 will bemaintained at or above the lower voltage limit of +24 volts, thepotential at the bottom of the primary of the transformer 37 will beapproximately +25 volts. This difference in voltage is required toovercome the diode drop of the diode 21. Since the bottom of the primaryof the transformer 37 is at approximately +25 volts and the top of theprimary has been dropped to +6 volts by the transient, the current inthe primary of the transformer 37 will now decrease because of thisreverse-bias across its primary. As the current decreases and reachesthe I, or lower current level of 10 amperes, the Hall device 101 willinitiate a sequence of operations, as previously described, to turn onthe transistor 159 and cause the bottom of the primary of thetransformer 37 to be near the ground potential while the top of theprimary of the transformer 37 remains at the +6-volt level. At this timethe current through the primary of the transformer 37 will start toincrease from the 10- to the IZ-ampere level but at a very slow rate,since the input voltage is now at a +6-volt level instead of the nominal+24-volt level. Each time the transistor 159 is turned off a newlZ-ampere pulse of current is fed from the primary of the transformer 37through the diode 21 into the parallel connected load 15 and capacitor25, with the current excess being used to increase the output voltagedeveloped across the capacitor 25. These l2-ampere pulses of currentwill cause the output voltage developed across the capacitor 25 toincrease until the upper voltage limit of 26 volts is reached orexceeded. When the upper voltage limit is reached, the voltage sensingcircuit 2'7 will operate in conjunction with the switching circuit 39 toturn on the transistor S and circulate in the secondary of thetransformer 37 the current that had built up there, until the outputvoltage has decreased to or below the +24-volt level. It should be notedat his time that the ratio of the l2-ampere pulses from the transformer37 to the 2 amperes required by the load 15 allows for a duty factorsmall enough to maintain the voltage at the output, even though theperiod between pulses is relatively long in relation to the pulsewidthof the l2-ampere pulses. When the total flux produced by the currentcirculating in the primary and secondary windings of the transformer 37decreases below the level representing 10 amperes of current in theprimary of the transformer 37, the current sensing circuit 41 causes theswitching circuit 40 to turn on the transistor 159 and replenish thecurrent flowing through the primary of the transformer 37.

At low input voltages of down to +6 volts, the energy stored in thetransformer 37 is barely sufficient to replenish the charge on thecapacitor 25 between the recharge cycles of the transformer 37. At inputvoltages above +24.7 volts, the energy is merely circulated for storagein order to be prepared for the time when a transient condition drivesthe input of the unregulated input voltage down to as low as a +6-voltlevel.

If the transient condition were such that the input voltage wasgradually changed from +26.7 volts down to +6 volts, a circulatingcurrent of from 10 to l2 amperes would not be needed. A system could bedesigned to circulate just 2 to 3 amrmres and gradually build up thecirculating current to supply a greater and greater charging current tothe capacitor 25 as the output voltage decreased. However, in manyoperations the transient occurs very suddenly, which would cause theoutput voltage to dip suddenly below the 24-volt level and thengradually recover as the current built up to the l2-ampere level, andthen recharged the capacitor 25. In contrast, the system of FIG. 5circulates a current of from 10 to 12 amperes at all times. As a result,whenever a transient appears between the input terminals 11 and 13 anddrops the input voltage to as low as +6 volts, that transient does notappear in the output voltage at all because of the ready availability ofthe charging current to maintain the output voltage developed by thecapacitor 25 between the limits of +24 to +26 volts at all times.

Noncompensated zener diodes such as zener diodes 109, M7 and have beenused in FIG. 5, since the voltage and sensing functions are onlyrequired to be crude for the particular application for which the powersupply of FIG. 5 was first used. If, for some reason, very precisevoltage and current sensing were required, then the diodes 109, 147, 185and some of the other zener diodes could be replaced with compensatedprecision zener diodes.

In accordance with the teachings of the invention as previouslydescribed, it is to be noted that if the anode of the diode 21 wereconnected to the junction of the secondary of the transformer 37 and theanode of the diode 164 instead of to the junction of the primaries ofthe transformers 37 and 161, the power supply could achieve outputvoltage regulation for input voltage levels higher or lower than theoutput voltage level.

Now referring to FIG. 6, the mechanization of the embodiment of FIG. 1is shown. In this embodiment the voltage sensing circuit 27 and thecurrent sensing circuit 17 are basically identical in structure,function and operation to those (27 and 41, respectively) illustratedand described in relation to FIG. 5 and therefore will not be discussedin detail. In this embodiment the inductor 19 is used instead of thetransformer 37 and the switching circuits 29 and 35 are designeddifferently than their respective switching circuits 39 and 40 in FIG.5. in this embodiment the Hall device FIG. 5) in the current sensingcircuit 17 is inserted in the core of the inductor 19 in order to sensethe ampere-turns and hence when the current through the inductor 19 hasdecreased to or below the I or lO-ampere level, or increased to or abovethe I or l2-ampere level, and accordingly, control the operation of theswitching circuit 35. The structure and operation of the switchingcircuit 35 are identical to those of the switching circuit 40 of FIG. 5with the exception of the addition of a twoinput AND-gate 301. One ofthe inputs of the AND-gate 301 is connected to the output of theinverter 135, while the output of the AND-gate 301 is coupled to theresistor 137. The other input to the AND-gate 301 is coupled to theswitching circuit 29. Whenever both inputs to the AND-gate 301 are in aone state or high voltage level, the AND-gate 301 produces a highvoltage or one state output, which causes the transistor 159 to beturned 05. The lower input to the AND- gate 301 is put in a one statewhen the current sensing circult 17 senses that the current through theinductor 19 has reached or exceeded the upper current level 1 of 12arnperes. The time of and reason for placing a zero state voltage signalon the upper part of the AND-gate 301 will be discussed later. When theoutput of the AND-gate 301 is in the zero state or low voltage level, aswhen the current sensing circuit 17 senses that the current flowingthrough the inductor .19 is at or below the low current level 1 of 12amperes, the transistor 159 is turned on so that the current through theinductor 19 can build back to the l2-ampere level.

When the output voltage across the capacitor 25 reaches or exceeds theupper voltage limit 13 of +26 volts, the voltage sensing circuit 27produces a zero state or a low voltage output which is applied throughthe resistor 303 to the base of NPN-transistor 305, causing thetransistor 305 to start conducting. The emitter of the transistor 305 isconnected directly to the output of the power supply and through aresistor 307 to the base of the transistor 305. Resistor 307 takes careof leakage currents and desensitizes the operation of the transistor 305for noise purposes. Upon being turned on, the transistor 305 conductsthrough resistor 309 and capacitor 311 to ground, causing the voltageacross the capacitor 311 to increase. The junction of the resistor 309and capacitor 311 is connected to the emitter of a unijunctiontransistor 313 which has one of its bases connected to the emitter ofthe transistor 305 and the other base coupled through the primary of atransformer 315 to ground. The unijunction transistor 313, the resistor309 and the capacitor 311 comprise a sawtooth generator. As is wellknown in the art, when the voltage across the capacitor 311 hasincreased to a level above the voltage gradient opposite the P-typematerial in the unijunction transistor 313, the PN-junction thereof willbe forward-biased and start conducting which will rapidly discharge thecapacitor 311 thereby cutting off the unijunction transistor 313, andthe cycle will repeat. Each time the unijunction transistor 313 isturned on a pulse of current is drawn through the primary of thetransformer 315. As a result, a train of pulses at a fairly highrepetition rate is coupled into the secondary winding of the transformer315, which is coupled between the gate and cathode electrodes of asilicon controlled rectifier (SCR) 317. The cathode-anode re ion of theSCR 317 is coupled across the inductor 19 with the cathode beingconnected to the input terminal 11. The train of pulses is supplied fromthe unijunction transistor circuit in order to assure that the SCR 317will trigger, if not on the first pulse, then on some subsequent pulse.As a result, under high voltage conditions as sensed by the voltagesensing circuit 27, the SCR 317 is gated on by this train of pulses inorder to provide a short across the inductor 19 so that the current cancirculate therethrough until the current is needed to charge thecapacitor 25 again. It should be noted that the cathode of the SQR 317is connected to the input terminal 11 so that when the transistor 159 isturned on under low current conditions, the anode of the SCR 317 is at alow potential thereby back-biasing the SCR 317 and preventing itsconduction.

A serially coupled inverter 319 and Ill-microsecond single shotmultivibrator 321 are coupled between the collector of thePNP-transistor 305 and the second input to the ANDgate 301. With adecrease in the output voltage to or below the +24-volt level, thevoltage sensing circuit produces a high output which turns oi? thetransistor 305, causing its collector to go to a low voltage state. Thislow voltage state from the collector of the transistor 305 is invertedby inverter 319 and the resultant inverted pulse is used to trigger thesingle-shot multivibrator 321. The multivibrator .321 then supplies anegative or zero state pulse of i microseconds in duration to theAND-circuit 1101, thereby initiating the sequence of operationpreviously discussed in order to turn on the transistor 159. This zerostate or low output voltage from the single-shot multivibrator 321 isapplied to the AND-gate 301 and used to turn on transistor 159. When thetransistor 159 turns on, it reversebiases the SCR 317, thereby removingthe short across the inductor 19 md allowing the current through theinductor 19 to be used to recharge the capacitor 25 to increase theoutput voltage.

in the embodiments shown in FIGS. 5 and 6 it is possible to eliminatethe Hall device and to replace it with some other form of currentsensing. In both embodiments the operation of the comparator 117 musthave a sufficiently large input common-mode dynamic range to accommodateinput transient signals from the input terminal 11, which can be atvoltages between +6 and volts, for example. In this event, the Halldevice 101 and its associated circuitry consisting of transistor 103,resistors 105 and 107 and zener diode 109, can be replaced with currentsensing resistor circuitry.

FIG. 7 reveals the modification for the embodiment of FIG. 6 wherein adifferent type of current sensing is utilized. The current sensingcircuit 17 (see current sensing circuit 41 of FIG. 5) is modified byeliminating the Hall device 101, the transistor 103, the zener diode 109and the resistors 105 and 107 and adding the current sensing resistorcircuitry 401, as shown. The remaining components of FIG. 7 have beenpreviously described in relation to FIG. 6. A current sensing resistor403 is serially connected between the input terminal 11, and theinductor 19 to develop a voltage thereacross which has an amplitudeproportional to the amplitude of the current flowing through theinductor 19. The resistor 403 may be, for example, 10 milliohms in size.

A differential amplifier 405, comprising the transistors 407 and 409 andthe resistors 411, 413, 415 and 417, is coupled across the sensingresistor 403 in order to translate the DC level across the sensingresistor 403 to ground. Since the unregulated DC input voltage at inputterminal 1 1 may vary from +6 volts to +90 volts, for example, withrespect to ground, the voltage on each side of the resistor 403 willalso vary at substantially these same levels. The translation of thevoltage at these levels is necessary in order to protect the comparator117 from damage.

Assume at this time that the input voltage at terminal 11 is at anominal +24 volts and the output voltage is at +25 volts and the switch35 is closed to allow the current through the indoctor 19 to increasefrom the I level to the I level. As the current in the inductor l9builds up from 10 to 12 amperes, the voltage drop across the seriallyconnected resistor 403 changes from 100 to l20 millivolts, with the sideof the re sistor 403 connected to terminal 11 being positive withrespect to the other side of the resistor. Since both of the transistors407 and 409 are forward-biased at this time, the transistor 409 willconduct via the resistors 413 and 417 to ground and the transistor 407will conduct via the resistors 411 and 415 to ground. However, thetransistor 409 will conduct more heavily than the transistor 407 sinceits forwardbias is greater than that of the transistor 407. As a resultthe voltage developed across the resistor 417 will be greater than thatdeveloped across the resistor 415. The voltage developed across theresistor 417 is applied via terminal 111 and resistor 115 to input pin 2of the comparator 117 while the voltage developed across the resistor415 is applied via terminal 110 and resistor 113 to input pin 3 of thecomparator 117. When the current flowing through the resistor 403 andthe inductor 19 has reached the 1 level of 12 amperes, the voltageapplied to pin 2 of the comparator 117 will exceed the voltage appliedto pin 3 and the crossover point will be reached. Therefore the voltageat output pin 7 of the comparator 117 will become sufficiently high tocause the zener diode to conduct which, as previously explained, willcause the switch 35 to be turned off to prevent the current from furtherincreasing.

In alike manner, when the current through the inductor 19 has decreasedto the 1 level of 10 amperes, the voltage at pin 3 will exceed thevoltage at pin 2 of the comparator 117 and cause the voltage at outputpin 7 of the comparator 117 to initiate the sequence of operation,previously described, to turn on the switch 35 to allow the current tobuild back up to the I level.

FIG. 8 shows how the embodiment of FIG. 5 can be modified to replace theHall device 161 with sensing resistors. Sensing resistors 421 and 423are respectively placed in series with the primary and secondarywindings of the transformer 37. Each of these resistors 421 and 423senses the current in its respective winding by developing a voltageacross its respective resistance in proportion to the current flowingtherethrough. A difierential amplifier or comparator 425, similar to thecomparator 117, has its input pins 2 and 3 connected across the resistor421 while its output pin '7 is coupled through resistor 427 to pin 2 ofthe comparator ll 17. The comparator 425 develops an output signalrelated to the differential signal developed across the resistor 421.The voltage developed by the resistor 423 is applied through resistor431 to pin 2 of the comparator 117. The resistors 427 and 431 areconnected together to form a summation network for summing the outputvoltage of the comparator 425 with the voltage developed across theresistor 423 and applying the sum to pin 2 of the comparator 117. Theother input to the comparator 117 is a reference voltage which isapplied to inverting input pin 3 in order to establish the crossoverpoint for the operation of the comparator 117. The output signal of thecomparator 117 is applied to the zener diode 125 for subsequent controlof the switching circuit 411, as previously described.

Referring now to FllG. 9, a third embodiment of the invention isillustrated. In this embodiment a transformer 501 is utilized which hasa primary winding 503 and secondary windings 505 and 507. With respectto the primary winding 503, the secondary windings 505 and 507 arerespectively illustrated to have stepdown and step-up turns ratios.Furthermore, as in dicated by the dots adjacent to the windings, theupper side of each of the secondary windings 505 and 507 has the samephase relationship as the lower side of the primary winding 503. Theupper side of the primary winding 503 is connected to an input terminal5119 and the lower side of the winding 503 is coupled through a switchor switching circuit 511, corresponding to the switch 411 in FIG. 4, toanother input terminal 513 for receiving an unregulated DC input voltagefrom the terminals 509 and 513.

A flux or current sensing circuit 515, similar to the current sensingcircuit 41 in FIG. 4, senses the flux in the core of the transformer501. The flux in the transformer core is proportional to the totalampere turns on the transformer 501. The output of this current sensingcircuit 515 controls the operation of the switch 511 by closing theswitch 511 when the flux being sensed is too low and by opening theswitch 511 when the flux is too high. Thus the current sensing circuit515 maintains the transformer ampere turns between predetermined upperand lower limits. The lower flux or ampere turn limit, as sensed by thecurrent sensing circuit 515, is chosen such that with the application ofa minimum input voltage when the switch 511 is closed, the total inputpower in the primary winding 503 will exceed the total output power ofthe voltage regulator by a factor greater than or equal to thereciprocal of the efficiency times the reciprocal of the maximum dutyfactor of the switch 511.

A serially coupled diode 517 and capacitor 519 combination is coupledacross the secondary winding 505 in order to provide an output regulatedDC voltage across the capacitor 519. The other secondary winding 5117has a serially coupled diode 521 and capacitor 523 combination coupledbetween a tap 524 on the winding 507 and the lower side of the winding507 in order to provide an output regulated DC voltage across thecapacitor 523 at a higher voltage level than the output voltagedeveloped across the capacitor 519. A diode 525 is coupled in serieswith a switch or switching circuit 527, similar to the switch 39 in FIG.4, with the combination thereof connected across the entire secondarywinding 507 in order to provide a loop for storing current when theregulated output voltage across the capacitor 523 is betweenpredetermined minimum and maximum voltage levels. A voltage sensingcircuit 529, similar to the voltage sensing circuit 27, is coupledacross the capacitor 523 in order to sense the output voltagethereacross. This voltage sensing circuit 529 controls the operation ofthe switch 527 in response to the sensed output voltage across thecapacitor 523, similar to the manner in which the voltage sensingcircuit 27 controlled the operation of the switch 29 in FIG. 1.

In initial operation when the unregulated input voltage is first appliedto the input terminals 509 and 513, the current sensing circuit 515senses that the flux in the core of the transformer 501 is low andtherefore causes the switch 511 to close. In addition, the voltagesensing circuit 529 causes the switch 527 to be open due to the lowvoltage output across the capacitor 523. With the switch 511 closed,current starts flowing through the primary winding 503 at a time ratedetermined by the inductance of the primary winding 503, therebybuilding up the flux in the core of the transformer 501. During the timethat the flux is building up, no power is being delivered from the inputdirectly to the outputs, since the diodes 517 and 521, as well as thediode 525, are reverse-biased, thereby preventing the capacitors 519 and523 from charging. Since the number of turns in the primary andsecondary windings is fixed, the increase in current flowing through theprimary winding 503 causes the ampere turns on the transformer 501 toincrease. This increase in the ampere turns causes the flux in thetransformer core to increase until the current sensing circuit 515senses that the flux in the transformer 501 has reached the upper limit,at which time the current sensing circuit 515 opens the switch 511. Theopening of the switch 511 causes the magnetic field or flux that hadbeen built up in the core of the transformer 501 to start collapsing,thereby inducing across the secondary windings 505 and 507 voltageswhich forward-bias the diodes 517 and 521. The diode 525 is notforward-biased at this time since the switch 527 is still open. At theinstant of time that the switch 511 is opened, the total number ofampere turns on the transformer 501 cannot change. Since the opening ofthe switch 51] reduces the primary ampere turns to zero, the number ofampere turns in the secondary windings immediately after the opening ofthe switch 511 must be equal to the number of ampere turns in theprimary winding 503 immediately before the opening of the switch 511. Asa result, the accumulation of ampere turns in.

the secondary windings 50S and 507 results in a current flowing from thelower portion of the secondary winding 507 through the tap 524 and theforward-biased diode 521 to charge the capacitor 523 and to deliverpower to the load (not shown) associated therewith. Also, current flowsfrom the secondary winding 505 through the forward-biased diode 517 tocharge the capacitor 519 and provide power to the load (not shown)associated therewith.

In the event that the voltage across the capacitor 523 does not reachthe upper voltage level, as sensed by the voltage sensing circuit 529,before the flux in the core of the transformer 501 has decreased to thelower flux limit, as sensed by the current sensing circuit 515, theswitch 511 will again be closed. The closure of the switch 511 allowscurrent to flow in the primary winding 503 to build the flux back up tothe upper flux limit, at which time the current sensing circuit 515 willagain open the switch 511, thereby causing current flow in the secondarywindings 505 and 507 to continue charging the respective capacitors 519and 523.

When the voltage across the capacitor 523 has increased to the uppervoltage level, the voltage sensing circuit 529 closes the switch 527,thus allowing current to circulate in the entire secondary winding 507through the diode 525 and closed switch 527 as long as the switch 511 isopen. The capacitors 523 and 519 then slowly discharge through theirrespective loads in order to provide power to these loads. it should benoted at this time that the voltage sensing circuit 529 is coupledacross that output (consisting of the capacitor 523 and its associatedload) which operationally has a more rapid decay (percentagewise) inoutput voltage with respect to time than any other output. Only oneother output, consisting of the capacitor 519 and its associated load,is illustrated. However, it should be realized that more than twosecondary windings can be utilized in conformance with the teachingsherein presented. Therefore, due to its load requirements the capacitor523 will discharge more rapidly than the capacitor 519. When thecapacitor 523 has discharged down to the lower voltage level, thevoltage sensing circuit 529 will open the switch 527, thereby allowingthe current that had been circulating through the entire secondarywinding 507 to be utilized, whenever the switch 511 is open, to rechargethe capacitor 523. Since 1) the multiple output voltages across thecapacitors 523 and 519 are limited in amplitude by the respective turnsratios of the lower portion of the secondary winding 507 and thesecondary winding 505 to the primary winding 503 and (2) the sensedoutput across the capacitor 523 was designed for the highest percentagedischarge rate, the lower portion of the secondary winding 507 willinitially receive all of the circulating current to recharge thecapacitor 523, after which the output across the capacitor 519 will berecharged. This sequential recharging of the two illustrated outputs(and such additional outputs across additional secondary windings as maybe required) will be such that when the switch 527 is again closed orturned on, all outputs will be at their respective desired voltages.

The operation of the voltage regulator of this third embodiment issimilar to the four states of operation of the embodiment of FIG. 1.Briefly, when the switch 511 is closed to increase the flux in the coreof the transformer 501, it doesnt matter whether the switch 527 is openor closed since all of the diodes 517, 525 and 521 are reverse-biased.When the switch 511 is open and the switch 527 is closed, current isbeing circulated in the secondary winding 507. When the switches 511 and527 are both open, the circulating current in the secondary winding 507is used to recharge the capacitor 523 to the upper voltage level, andthe capacitor 519 is also charged through the secondary winding 505.When the voltage across the capacitor 523 has increased to the uppervoltage level, the voltage sensing circuit 529 closes the switch 527,enabling current to be circulated through the entire secondary winding507 as long as the switch 511 is open. The output voltage levels, assensed by the voltage sensing circuit 529 across the capacitor 523, canbe set arbitrarily close together, depending upon how high a switchingfrequency can be tolerated by the power supply or how high a rippleamplitude can be tolerated by the load.

Care should be taken that the number of turns across the secondarywinding 507 is such that the induced voltage across the entire secondarywinding 507 does not exceed the breakdown voltage of the switch 527 whenthe other output voltages are within their normal regulated ranges.However, the higher the voltage induced in the secondary winding 507,the smaller the current that has to circulate through the secondarywinding 507 in order to keep the same number of ampere turns that isoperationally required. The tap on the secondary winding 507 ispositioned to that point along the secondary winding which will allowthe desired output voltage to be developed across the capacitor 523.

It should be further noted that other flux or current sensing devicesmay be used in lieu of the current sensing circuit 515, which asspecified before may be similar to the current sensing circuit 41 inFIG. 4. For example, circuitry similar to that shown in H6. 8, may beused to sample the current flow in all of the windings of thetransformer 50! in order to determine the total flux in the core of thetransformer 501.

The invention thus provides, in one embodiment, a regulated power supplysystem for supplying to a load a relatively constant direct currentoutput voltage which is at a voltage level equal to or greater than thatsupplied from a variable DC source. In another embodiment a multiplicityof difi'erent regulated output voltages are derived, each being isolatedfrom the unregulated input voltage. The system stores a circulatingcurrent, which is maintained at a level within a predetermined range,until it is needed to increase the output voltage from a first to asecond predetermined level. After the circulating current has increasedthe output voltage to the second predetermined level, the current isstored until needed again. The wide effective bandwidth of the powersupply eliminates a transient efiect on the output voltage for anytransient change of input voltage within the dynamic range of the powersupply.

While the salient features have been illustrated and described withrespect to three particular embo;iments, it should be readily apparentto those skilled in the an that modifications can be made within thespirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A power supply for supplying regulated power to a load comprising:

current generator means, coupled to the load and adapted to receive aninput unregulated voltage, for supplying a current at least equal inamplitude to the maximum current required by the load;

input means coupled to said current generator means for sensing thecurrent through said current generator means, said input means beingresponsive to current at a lower current level through said currentgenerator means for providing a path for the current through saidcurrent generator means to increase to an upper current level, saidinput means being responsive to current at the upper current levelthrough said current generator means for coupling said current generatormeans to the load to allow said current generator means to increase theoutput voltage as needed;

output means, coupled to said current generator means and to the load,for sensing the amplitude of the output voltage across the load, saidoutput means being responsive to the upper voltage level of the sensedoutput voltage for preventing said current generator means fromsupplying current to the load, said output means being responsive to thelower voltage level of the sensed output voltage for allowing saidcurrent gencrator means to supply a current to the load, said outputmeans including:

a capacitor coupled across the load and being responsive to the currentsupplied by said current generator means for developing the outputvoltage for the load;

a voltage sensing circuit coupled to the load for sensing the amplitudeof the output voltage developed across said capacitor; and

a first switching circuit coupled to said current generator means andbeing controlled by said voltage sensing circuit to close when theoutput voltage has increased to at least the upper voltage level and toopen when the output voltage has decreased to at least the lower voltagelevel, said current generator means being bypassed back to itselfthrough the closure of said first switching circuit by said voltagesensing circuit when the output voltage has increased to at least theupper voltage level in order to prevent said capacitor from charging toa higher output voltage.

2. The power supply of claim 1 wherein said input means includes:

a current sensing circuit coupled to said current generator means forsensing the amplitude of the current through said current generatormeans;

a second switching circuit coupled to said current generator means andsaid voltage sensing circuit and being controlled by said currentsensing circuit to close and provide a path for increasing the currentthrough said current generator means when the current through saidcurrent generator means has decreased to at least the lower currentlevel and to open when the current through said current generator meanshas increased to at least the upper current level; and

diode means coupled between said second switching circuit and the loadand having conductive and nonconductive states, said diode means beingin the conductive state to allow current from said current generatormeans to pass therethrough to charge said capacitor to a higher outputvoltage when said second switching circuit is open, said diode meansbeing in a nonconductive state to prevent said capacitor fromdischarging through said second switching circuit when said secondswitching circuit is closed.

3. The power supply of claim 2 wherein the current flowing through saidcurrent generator means produces a magnetic field having a strengthproportional to the amplitude of the current therethrough and saidcurrent sensing circuit includes:

a device placed in the magnetic field of said current generator means tosense the strength of the magnetic field in order to develop a firstvoltage having an amplitude proportional to the amplitude of the currentflowing through said current generator means; and

amplifier means coupled between said device and said second switchingcircuit and being responsive to the first voltage of said device fordeveloping a signal to close said second switching circuit when thecurrent through said current generator means has decreased to at leastthe lower current level and to open said second switching circuit whenthe current through said current generator means has increased to atleast the upper current level.

4. The power supply of claim 3 wherein said current generator means isan inductor.

5. The power supply of claim 3 wherein said current generator means is atransformer having a primary winding and a secondary winding, saidprimary winding coupled to said second switching circuit and saidsecondary winding coupled to said first switching circuit, said devicebeing inserted in the magnetic field produced by current flowing throughsaid primary and secondary windings of said transformer in order tosense the total strength of said magnetic field and control said secondswitching circuit as a function of the total magnetic field beingsensed.

6. The power supply of claim 2 wherein said current generator means isan inductor and said current sensing circuit ineludes:

a sensing resistor coupled in series with said inductor;

a differential amplifier coupled across said sensing resistor fordeveloping an output voltage proportional to the amplitude of currentflowing through said inductor; and

amplifier means coupled between the output of said differentialamplifier and said second switching circuit and being responsive to theoutput of said differential amplifier for developing a signal to closesaid second switching circuit when the current through said inductor hasdecreased to at least the lower current level and to open said secondswitching circuit when the current through said inductor has increasedto at least the upper current level.

7. The power supply of claim 2 wherein:

said current generator means includes a transformer having a primarywinding and a secondary winding, said primary winding coupled to saidsecond switching circuit and said secondary winding coupled to saidfirst switching circuit; and

said current sensing circuit includes first and second sensing resistorsserially coupled to said primary and secondary windings respectively forrespectively developing voltages indicative of the amplitudes ofcurrents flowing through said primary and secondary windings, first andsecond differential amplifier circuits each having input and outputcircuits, said input circuit of said first differential amplifiercircuit being coupled across said first sensing resistor to develop afirst voltage related to the amplitude of the current flowing throughsaid primary winding, first means coupled to the output of said firstdifferential amplifier and to said second sensing resistor fordeveloping a second voltage related to the amplitude of the totalcurrent flowing through said primary and secondary windings, said inputcircuit of said second differential amplifier being adapted to receive areference voltage and the second voltage in order to develop a thirdvoltage for controlling the operation of said second switching circuit.

it. A regulated power supply comprising:

first storage means for storing voltage;

second storage means for storing current;

first circuit means coupled to said first storage means for sensing theamplitude of voltage stored by said first storage means;

first switching circuit means coupled to said second storage means andcontrolled by said first circuit means to allow the stored current to beused to increase the amplitude of the stored voltage when the storedvoltage has decreased to at least a lower voltage level and to preventthe stored current from being used to further increase the amplitude ofthe stored voltage when the stored voltage has increased to at least anupper voltage level;

second circuit means coupled to said second storage means for sensingthe amplitude of the current stored by said second storage means; and

second switching circuit means coupled to said second storage means andcontrolled by said second circuit means for selectively allowing theamplitude of the current in said second storage means to be maintainedwithin first and second predetermined current limits.

9. A power supply for supplying regulated power to a load comprising:

current generator means, coupled to the load and adapted to receive aninput unregulated voltage, for' supplying a current at least equal inamplitude to the maximum current required by the load;

a capacitor coupled to said current generator means and across the loadand being responsive to the current supplied by said current generatormeans for developing the output voltage for the load;

a voltage sensing circuit coupled to the load for sensing the amplitudeof the output voltage developed across said capacitor;

a first switching circuit coupled to said current generator means andbeing controlled by said voltage sensing circuit to close when theoutput voltage has increased to at least the upper voltage level and toopen when the output voltage has decreased to at least the lower voltagelevel, said current generator means being bypassed back to itselfthrough the closure of said first switching circuit by said voltagesensing circuit when the output voltage has increased to at least theupper voltage level in order to prevent said capacitor from charging toa higher output voltage;

a current sensing circuit coupled to said current generator means forsensing the amplitude of the current through said current generatormeans;

a second switching circuit coupled to said current generator means, saidsecond switching circuit being controlled by said current sensingcircuit to close and provide a path to increase the amplitude of currentthrough said current generator means when the current through saidcurrent generator means has decreased to at least the lower currentlevel and to open when the current through said current generator meanshas increased to at least the upper current level; and

diode means coupled between said current generator means and the loadfor allowing current from said current generator means to charge saidcapacitor to a higher output voltage when said first and secondswitching circuits are open.

10. The power supply of claim 9 wherein:

said current generator means includes a transformer having a primarywinding and a secondary winding, said primary winding coupled to saidsecond switching circuit and said secondary winding coupled to saidfirst switching circuit; and

said current sensing circuit includes first and second sensing resistorsserially coupled to said primary and secondary windings respectively forrespectively developing voltages indicative of the amplitudes ofcurrents flowing through said primary and secondary windings, first andsecond differential amplifier circuits each having input and outputcircuits, said input circuit of said first differential amplifiercircuit being coupled across said first sensing resistor to develop afirst voltage related to the amplitude of the current flowing throughsaid primary winding, first means coupled to the output of said firstdifferential amplifier and to said second sensing resistor fordeveloping a second voltage related to the amplitude of the totalcurrent flowing through said primary and secondary windings, said inputcircuit of said second difi'erential amplifier being adapted to receivea reference voltage and the second voltage in order to develop a thirdvoltage for controlling the operation of said second switching circuit.

1 1. The power supply of claim 9 wherein the currents flowing throughsaid current generator means produces a magnetic field having a strengthproportional to the amplitudes of the currents therethrough and saidcurrent sensing circuit includes:

a device placed in the magnetic field of said current generator means tosense the strength of the magnetic field in order to develop a firstvoltage having an amplitude proportional to the amplitudes of thecurrents flowing through said current generator means; and amplifiermeans coupled between said device and said second switching circuit andbeing responsive to the first voltage of said device for developing asignal to close said second switching circuit when the currents throughsaid current generator means has decreased to at lemt the lower currentlevel and to open said second switching circuit when the currentsthrough said current generator means has increased to at least the uppercurrent level.

12. The power supply of claim 11 wherein said current generator means isa transformer having a primary winding and secondary winding means forreceiving energy from said primary winding, said primary winding coupledto said second switching circuit and said secondary winding meanscoupled to said first switching circuit, said device being inserted inthe magnetic field produced by current flowing through said primarywinding and said secondary winding means of said transformer in order tosense the total strength of said magnetic field and control said secondswitching circuit as a function of the total magnetic field beingsensed.

1. A power supply for supplying regulated power to a load comprising:current generator means, coupled to the load and adapted to receive aninput unregulated voltage, for supplying a current at least equal inamplitude to the maximum current required by the load; input meanscoupled to said current generator means for sensing the current throughsaid current generator means, said input means being responsive tocurrent at a lower current level through said current generator meansfor providing a path for the current through said current generatormeans to increase to an upper current level, said input means beingresponsive to current at the upper current level through said currentgenerator means for coupling said current generator means to the load toallow said current generator means to increase the output voltage asneeded; output means, coupled to said current generator means and to theload, for sensing the amplitude of the output voltage across the load,said output means being responsive to the upper voltage level of thesensed output voltage for preventing said current generator means fromsupplying current to the load, said output means being responsive to thelower voltage level of the sensed output voltage for allowing saidcurrent generator means to supply a current to the load, said outputmeans including: a capacitor coupled across the load and beingresponsive to the current supplied by said current generator means fordeveloping the output voltage for the load; a voltage sensing circuitcoupled to the load for sensing the amplitude of the output voltagedeveloped across said capacitor; and a first switching circuit coupledto said current generator means and being controlled by said voltagesensing circuit to close when the output voltage has increased to atleast the upper voltage level and to open when the output voltage hasdecreased to at least the lower voltage level, said current generatormeans being bypassed back to itself through the closure of said firstswitching circuit by said voltage sensing circuit when the outputvoltage has increased to at least the upper voltage level in order toprevent said capacitor from charging to a higher output voltage.
 2. Thepower supply of claim 1 wherein said input means includes: a currentsensing circuit coupled to said current generator means for sensing theamplitude of the current through said current generator means; a secondswitching circuit coupled to said current generator means and saidvoltage sensing circuit and being controlled by said current sensingcircuit to close and provide a path for increasing the current throughsaid current generator means when the current through said currentgenerator means has decreased to at least the lower current level and toopen when the current through said current generator means has increasedto at least the upper current level; and diode means coupled betweensaid second switching circuit and the load and having conductive andnonconductive states, said diode means being in the conductive state toallow current from said current generator means to pass therethrough tocharge said capacitor to a higher output voltaGe when said secondswitching circuit is open, said diode means being in a nonconductivestate to prevent said capacitor from discharging through said secondswitching circuit when said second switching circuit is closed.
 3. Thepower supply of claim 2 wherein the current flowing through said currentgenerator means produces a magnetic field having a strength proportionalto the amplitude of the current therethrough and said current sensingcircuit includes: a device placed in the magnetic field of said currentgenerator means to sense the strength of the magnetic field in order todevelop a first voltage having an amplitude proportional to theamplitude of the current flowing through said current generator means;and amplifier means coupled between said device and said secondswitching circuit and being responsive to the first voltage of saiddevice for developing a signal to close said second switching circuitwhen the current through said current generator means has decreased toat least the lower current level and to open said second switchingcircuit when the current through said current generator means hasincreased to at least the upper current level.
 4. The power supply ofclaim 3 wherein said current generator means is an inductor.
 5. Thepower supply of claim 3 wherein said current generator means is atransformer having a primary winding and a secondary winding, saidprimary winding coupled to said second switching circuit and saidsecondary winding coupled to said first switching circuit, said devicebeing inserted in the magnetic field produced by current flowing throughsaid primary and secondary windings of said transformer in order tosense the total strength of said magnetic field and control said secondswitching circuit as a function of the total magnetic field beingsensed.
 6. The power supply of claim 2 wherein said current generatormeans is an inductor and said current sensing circuit includes: asensing resistor coupled in series with said inductor; a differentialamplifier coupled across said sensing resistor for developing an outputvoltage proportional to the amplitude of current flowing through saidinductor; and amplifier means coupled between the output of saiddifferential amplifier and said second switching circuit and beingresponsive to the output of said differential amplifier for developing asignal to close said second switching circuit when the current throughsaid inductor has decreased to at least the lower current level and toopen said second switching circuit when the current through saidinductor has increased to at least the upper current level.
 7. The powersupply of claim 2 wherein: said current generator means includes atransformer having a primary winding and a secondary winding, saidprimary winding coupled to said second switching circuit and saidsecondary winding coupled to said first switching circuit; and saidcurrent sensing circuit includes first and second sensing resistorsserially coupled to said primary and secondary windings respectively forrespectively developing voltages indicative of the amplitudes ofcurrents flowing through said primary and secondary windings, first andsecond differential amplifier circuits each having input and outputcircuits, said input circuit of said first differential amplifiercircuit being coupled across said first sensing resistor to develop afirst voltage related to the amplitude of the current flowing throughsaid primary winding, first means coupled to the output of said firstdifferential amplifier and to said second sensing resistor fordeveloping a second voltage related to the amplitude of the totalcurrent flowing through said primary and secondary windings, said inputcircuit of said second differential amplifier being adapted to receive areference voltage and the second voltage in order to develop a thirdvoltage for controlling the operation of said second switching circuit.8. A regulated power supply comprising: first storage means for storingvoltage; second storage means for storing current; first circuit meanscoupled to said first storage means for sensing the amplitude of voltagestored by said first storage means; first switching circuit meanscoupled to said second storage means and controlled by said firstcircuit means to allow the stored current to be used to increase theamplitude of the stored voltage when the stored voltage has decreased toat least a lower voltage level and to prevent the stored current frombeing used to further increase the amplitude of the stored voltage whenthe stored voltage has increased to at least an upper voltage level;second circuit means coupled to said second storage means for sensingthe amplitude of the current stored by said second storage means; andsecond switching circuit means coupled to said second storage means andcontrolled by said second circuit means for selectively allowing theamplitude of the current in said second storage means to be maintainedwithin first and second predetermined current limits.
 9. A power supplyfor supplying regulated power to a load comprising: current generatormeans, coupled to the load and adapted to receive an input unregulatedvoltage, for supplying a current at least equal in amplitude to themaximum current required by the load; a capacitor coupled to saidcurrent generator means and across the load and being responsive to thecurrent supplied by said current generator means for developing theoutput voltage for the load; a voltage sensing circuit coupled to theload for sensing the amplitude of the output voltage developed acrosssaid capacitor; a first switching circuit coupled to said currentgenerator means and being controlled by said voltage sensing circuit toclose when the output voltage has increased to at least the uppervoltage level and to open when the output voltage has decreased to atleast the lower voltage level, said current generator means beingbypassed back to itself through the closure of said first switchingcircuit by said voltage sensing circuit when the output voltage hasincreased to at least the upper voltage level in order to prevent saidcapacitor from charging to a higher output voltage; a current sensingcircuit coupled to said current generator means for sensing theamplitude of the current through said current generator means; a secondswitching circuit coupled to said current generator means, said secondswitching circuit being controlled by said current sensing circuit toclose and provide a path to increase the amplitude of current throughsaid current generator means when the current through said currentgenerator means has decreased to at least the lower current level and toopen when the current through said current generator means has increasedto at least the upper current level; and diode means coupled betweensaid current generator means and the load for allowing current from saidcurrent generator means to charge said capacitor to a higher outputvoltage when said first and second switching circuits are open.
 10. Thepower supply of claim 9 wherein: said current generator means includes atransformer having a primary winding and a secondary winding, saidprimary winding coupled to said second switching circuit and saidsecondary winding coupled to said first switching circuit; and saidcurrent sensing circuit includes first and second sensing resistorsserially coupled to said primary and secondary windings respectively forrespectively developing voltages indicative of the amplitudes ofcurrents flowing through said primary and secondary windings, first andsecond differential amplifier circuits each having input and outputcircuits, said input circuit of said first differential amplifiercircuit being coupled across said first sensing resistor to develop afirst voltage related to the amplitude of the current flowing throughsaid primary winding, first meAns coupled to the output of said firstdifferential amplifier and to said second sensing resistor fordeveloping a second voltage related to the amplitude of the totalcurrent flowing through said primary and secondary windings, said inputcircuit of said second differential amplifier being adapted to receive areference voltage and the second voltage in order to develop a thirdvoltage for controlling the operation of said second switching circuit.11. The power supply of claim 9 wherein the currents flowing throughsaid current generator means produces a magnetic field having a strengthproportional to the amplitudes of the currents therethrough and saidcurrent sensing circuit includes: a device placed in the magnetic fieldof said current generator means to sense the strength of the magneticfield in order to develop a first voltage having an amplitudeproportional to the amplitudes of the currents flowing through saidcurrent generator means; and amplifier means coupled between said deviceand said second switching circuit and being responsive to the firstvoltage of said device for developing a signal to close said secondswitching circuit when the currents through said current generator meanshas decreased to at least the lower current level and to open saidsecond switching circuit when the currents through said currentgenerator means has increased to at least the upper current level. 12.The power supply of claim 11 wherein said current generator means is atransformer having a primary winding and secondary winding means forreceiving energy from said primary winding, said primary winding coupledto said second switching circuit and said secondary winding meanscoupled to said first switching circuit, said device being inserted inthe magnetic field produced by current flowing through said primarywinding and said secondary winding means of said transformer in order tosense the total strength of said magnetic field and control said secondswitching circuit as a function of the total magnetic field beingsensed.